docs: def get_nbytes(self):
          """ Compute and return the object size in bytes (i.e.: octets)
  
          A flat dict containing all the objects attributes is first created
          The size of each attribute is then estimated with np.asarray().nbytes
  
          Note :
              if the attribute is a tofu object, get_nbytes() is recursive
  
          Returns
          -------
          total :     int
              The total object estimated size, in bytes
          dsize :     dict
              A dictionnary giving the size of each attribute
          """
          dd = self.to_dict()
          dsize = dd.fromkeys(dd.keys(),0)
          total = 0
          for k, v in dd.items():
              if issubclass(v.__class__, ToFuObjectBase):
                  dsize[k] = v.get_nbytes()[0]
              else:
                  dsize[k] = np.asarray(v).nbytes
              total += dsize[k]
          return total, dsize